In recent years, various types of nickel-metal hydride storage batteries have been proposed as power sources for portable devices or equipment or power sources for electric vehicles or hybrid electric vehicles. In such nickel-metal hydride storage batteries, a resin case made of resin or a metal case made of metal is used as a case (a battery casing) (refer to e.g. Patent documents 1 and 2).
Patent document 1: Japanese unexamined patent publication No. 8-148135 (1996)
Patent document 2: Japanese unexamined patent publication No. 8-31398 (1996)
The nickel-metal hydride storage battery is normally designed to have a negative electrode capacity larger than a positive electrode capacity. Accordingly, the discharge capacity of the battery is regulated by the positive electrode capacity (hereinafter, referred to as a “positive electrode capacity regulation”). This positive electrode regulation makes it possible to suppress an increase in internal pressure during overcharging or overdischarging. It is to be noted that an excess capacity of a negative electrode available for charge is referred to as charge reserve and an excess capacity of the negative electrode available for discharge is referred to as discharge reserve.